Syringe having safety needle shield

Abstract

A safety syringe assembly includes a hypodermic syringe having a syringe barrel with opposed proximal and distal ends. A needle cannula is mounted to the distal end of the barrel. A collar mounted around the syringe barrel includes at least one radially inwardly directed recess. A safety shield is positioned over the syringe barrel for telescoping movement from a proximal position where the needle cannula is exposed to a distal position where the syringe safety shield protectively surrounds the needle cannula. The safety shield is rotatable with respect to the barrel when the safety shield is in its proximal position. The safety shield includes an inside surface having at least one inwardly directed projection sized and positioned to pass through the recess in the collar when the safety shield is rotated with respect to the barrel to align the projection and the recess. When alignment is achieved the safety shield can be moved form the proximal position to the distal position. The collar and the projection prevent movement of the safety shield from the proximal position when the projection and the recess are not aligned.

What is claimed is: 
     
       1. A safety syringe assembly comprising: a hypodermic syringe having a syringe barrel with opposed proximal and distal ends, said distal end of said syringe barrel having a needle cannula mounted thereto;   a collar mounted around said syringe barrel, said collar including at least one radially inwardly directed recess;   a safety shield positioned over said syringe barrel for telescoping movement from a proximal position where said needle cannula is exposed to a distal position where said safety shield protectively surrounds said needle cannula, said safety shield being rotatable with respect to said barrel when said safety shield is in said proximal position, said safety shield having an inside surface including at least one inwardly directed projection sized and positioned to pass through said recess in said collar when safety shield is rotated with respect to said barrel to align said projection and said recess and said safety shield is moved from said proximal position toward said distal position, said collar and said projection preventing movement of said safety shield from said proximal position when said projection and said recess are not aligned; and   means for locking engagement of said collar and said safety shield for locking said safety shield in said distal position wherein said locking engagement can be achieved with only axial movement of said safety shield distally with respect to said barrel.   
     
     
       2. The safety syringe assembly of claim 1 wherein said at least one projection includes four substantially equally spaced projections and said at least one recess includes four substantially equally spaced recesses. 
     
     
       3. The safety syringe assembly of claim 1 wherein said collar includes at least one radially directed protuberance positioned to block motion of said projection as said shield is rotated with respect to said collar for limiting rotation to less than 360 degrees. 
     
     
       4. The safety syringe assembly of claim 3 wherein said at least one protuberance includes at least two protuberances positioned about 90 degrees from each other for limiting the rotation of said safety shield with respect to said collar to equal or less than 90 degrees. 
     
     
       5. The safety syringe assembly of claim 3 wherein said at least one protuberance includes four protuberances. 
     
     
       6. The safety syringe assembly of claim 1 wherein said means for locking includes said collar having a stop wall projecting outwardly from said syringe barrel and at least one deflectable lock wall projecting distally and outwardly from said collar; and said safety shield including at least one stop block projecting inwardly therefrom, said stop block being engageable with said stop wall of said collar for preventing removal of said safety shield from said syringe barrel when said shield is in said distal position, said safety shield further comprising at least one locking tooth dimensioned and disposed to generate inward deflection of said lock wall of said collar during said telescoping movement of said safety shield from said proximal position toward said distal position, said locking tooth being spaced distally from said stop block a sufficient distance to enable engagement of said lock wall and said stop wall of said collar between said locking tooth and stop block of said safety shield, and said locking tooth configured to lockably engage said deflectable lock wall to prevent proximal movement of said safety shield from its locked distal position.   
     
     
       7. The safety syringe assembly of claim 6 wherein said at least one projection on said safety shield is positioned on said safety shield so that when said safety shield is in said proximal position said at least one projection pushes against said lock wall until said safety shield is rotated with respect to said barrel to align said at least one projection and said at least one groove. 
     
     
       8. The safety syringe assembly of claim 7 wherein said syringe barrel includes a finger flange at said proximal end of said barrel and said safety shield contacting said finger flange when said safety shield is in said proximal position. 
     
     
       9. The safety syringe assembly of claim 1 wherein said at least one recess in said collar is shaped to prevent continual rotation of said safety shield in the same direction with respect to said collar after said projection in said safety shield is aligned with and in said recess in said collar. 
     
     
       10. The safety syringe assembly of claim 1 wherein said collar includes an inner circumferential surface comprising a plurality of inwardly and distally directed barbs for biting into the syringe barrel for preventing proximal-to-distal removal of said collar from said syringe barrel. 
     
     
       11. The safety syringe assembly of claim 6, wherein said deflectable lock wall is a continuous frusto-conically-shaped wall except for said at least one recess. 
     
     
       12. The safety syringe assembly of claim 6, wherein said deflectable lock wall of said collar comprises a plurality of independently deflectable spaced apart locking wall segments projecting distally and outwardly from said collar. 
     
     
       13. The safety syringe assembly of in claim 6, wherein said deflectable lock wall of said collar includes a generally concavely tapered distal end for generating outward deflection of said lock wall in response to proximally directed forces exerted thereon. 
     
     
       14. The safety syringe assembly of claim 13, wherein said concavely tapered distal end of said lock wall defines a frusto-conically-shaped surface inclined at an angle of approximately 30 degrees with a radius of said collar. 
     
     
       15. The safety syringe assembly of claim 13, wherein said locking tooth of said safety shield includes a proximal end tapered for generating outward deflection of said lock wall of said collar in response to proximally directed forces of said locking tooth on said deflectable lock wall. 
     
     
       16. The safety syringe assembly of claim 6, wherein said safety shield includes opposed proximal and distal ends, said at least one stop block comprises a plurality of circumferentially spaced stop blocks generally adjacent said proximal end of said safety shield, and wherein said at least one locking tooth comprises a plurality of circumferentially spaced locking teeth. 
     
     
       17. The safety syringe assembly of claim 6, wherein said locking tooth is ramped to generate inward deflection of said locking wall of said locking collar in response to distally directed telescoped movement of said safety shield from said proximal position on said syringe barrel to said locked distal position.